Device and method for determining the position of two coupled shafts with respect to each other

Abstract

The invention relates to a device for determining the position of a first shaft ( 10 ) and of a second shaft ( 12 ) that is joined to the first shaft by means of a coupling ( 14 ), with respect to each other, having a first measurement unit being placed on a circumferential surface of the first shaft and a second measurement unit being placed on a circumferential surface of the second shaft, wherein at least one of the two measurement units has means ( 20 ) for producing at least one light beam bundle ( 22 ) and at least one of the two measurement units has detection means ( 24, 25, 26 ) in order to detect the impingement position of the light beam bundle on at least one detection area ( 24, 25, 26 ).

What is claimed is: 
     
       1. A device for determining the position of a first shaft and of a second shaft that is joined to the first shaft by means of a coupling, comprising:
 a first measurement unit being placed on a circumferential surface of the first shaft, a second measurement unit being placed on a circumferential surface of the second shaft, as well as an analysis unit; 
 wherein at least one of the two measurement units has means for producing at least one light beam bundle and at least one of the two measurement units has detection means for detecting data relating to the impingement position of the light beam bundle on at least one detection area; 
 wherein at least one of the two measurement units comprises at least one biaxial accelerometer sensor or gyroscope sensor for detecting the angle of rotation of the shafts; 
 wherein the analysis unit determines respective angle-of-rotation position, angular velocity, and angular acceleration of the shafts in a plurality of measured positions from the sensor data and determines the respective impingement position of the light beam bundle on the at least one detection area from the data supplied by the detection means, and determines the offset of the shafts from at least a part of the determined impingement positions by curve fitting; 
 and wherein the analysis unit is configured to perform a quality rating of the associated data for each of the individual measured positions based on at least the following criteria:
 angular velocity and angular acceleration, 
 difference between the tangential component of the impingement position(s) and the tangential component of the impingement position(s) of the preceding measured position, in relation to the time interval from the preceding measured position, 
 degree of deviation of the impingement position(s) from a curve fitted to at least a part of the determined impingement positions; 
 
 and to exclude data of a measured position from being taken into consideration in determining the shaft offset or to take data into consideration only with reduced weighting if the quality rating of these data lies below a threshold value. 
 
     
     
       2. The device according to  claim 1 , wherein the at least one sensor detects vibrations for each measured position, with the respective vibration intensity being a further criterion in evaluating quality of the data, a greater vibration intensity having a lower quality rating compared to a lower vibration intensity. 
     
     
       3. The device according to  claim 1 , wherein the analysis unit includes the time interval between the measured position and a reference time point of the rotational movement as a further criterion in evaluating quality of the data. 
     
     
       4. The device according to  claim 3 , wherein the reference time point is the start of the rotational movement, with a greater interval from the start of the rotational movement has a higher quality rating compared to a lesser interval from the start of rotational movement. 
     
     
       5. The device according to  claim 1 , wherein the analysis unit includes the time change of the angular acceleration as a further criterion in evaluating the quality of the data. 
     
     
       6. The device according to  claim 5 , wherein a greater time change of the angular acceleration has a lower quality rating compared to a lesser time change of the angular acceleration. 
     
     
       7. The device according to  claim 1 , wherein a higher angular velocity has a lower quality rating compared to a lower angular velocity. 
     
     
       8. The device according to  claim 1 , wherein a higher angular acceleration has a lower quality rating compared to a lower angular acceleration. 
     
     
       9. The device according to  claim 1 , wherein a greater difference between the tangential component of the impingement position and the impingement position of the preceding measured position, in relation to the time interval from the preceding measured position, has a lower quality rating compared to a lesser difference between the tangential component of the impingement position and the impingement position of the preceding measured position. 
     
     
       10. The device according to  claim 1 , wherein measured positions included in the curve fitting with lesser weighting have a lower quality rating compared to measured positions included in the curve fitting with greater weighting. 
     
     
       11. The device according to  claim 1 , wherein the analysis unit, after traversing a predetermined number of measured positions, a quality rating of the data of the measured positions traversed is performed on the basis of the quality rating of the individual measured positions to perform a curve fitting based on the measured positions traversed, and to output a message regarding the quality rating that has been determines. 
     
     
       12. The device according to  claim 11 , wherein the content of the message is either the termination or continuation of the measurement depending on whether the quality rating determined has or has not reached a predetermined threshold value. 
     
     
       13. The device according to  claim 11 , wherein the analysis unit is configured such that the angle-of-rotation distribution of the measured positions and the number of measured positions are used for determining the quality rating. 
     
     
       14. The device according to  claim 11 , wherein the mean deviation of the impingement positions from the fitted curve is used for determining the quality rating. 
     
     
       15. The device according to  claim 1 , wherein at least one of the two measurement units comprises two accelerometer sensors. 
     
     
       16. The device according to  claim 1 , wherein at least one sensor is an accelerometer sensor configured and arranged as a microeltectromechanical systems component. 
     
     
       17. The device according to  claim 1 , wherein each of the two measurement units is provided with at least one of the sensors, with the analysis unit determining the coupling play from the difference between the angle-of-rotation position determined with the data of the at least one sensor of the first measurement unit and the angle-of-rotation position determined with the data of the at least one sensor of the second measurement unit and to take this difference into consideration when determining the quality rating. 
     
     
       18. The device according to  claim 1 , wherein the detection means is at least one biaxial optical detector. 
     
     
       19. The device according to  claim 1 , wherein the detection area is a scattering area and the detection means is a camera, the camera capturing images of a side of the scattering area facing a side of impingement of the light beam bundle. 
     
     
       20. The device according to  claim 1 , wherein the detection area is a matte screen and the detection means is a camera, the camera capturing images of a side of the matte screen facing away from a side of impingement of the light beam bundle. 
     
     
       21. The device according to  claim 1 , wherein the first measurement unit includes means for producing the at least one light beam bundle and the second measurement unit includes detection means, the detection means having a first and a second detection area, the second detection area being optically offset in the axial direction in relation to the first detection area, and the two detection areas being impinged simultaneously by at least a part of the light beam bundle. 
     
     
       22. The device according to  claim 21 , further comprising:
 a beam splitter connected upstream to the first detection area to direct a part of the light beam bundle onto the second detection area. 
 
     
     
       23. The device according to  claim 21 , wherein the radial component of the respective impingement position on each of the two detection areas is employed for the curve fitting. 
     
     
       24. The device according to  claim 23 , wherein the radial component of the impingement position on the first detection area and the difference between the radial components of the impingement positions on the first and the second detection areas are employed for the curve fitting. 
     
     
       25. The device according to  claim 1 , wherein the first measurement unit includes means for producing the at least one light beam bundle and the detection means, with the second measurement unit having a reflector arrangement, which faces the first measurement unit when the measurement units are placed on the respective shaft to reflect the light beam bundle onto the detection area. 
     
     
       26. The device according to  claim 25 , wherein the radial component and the tangential component of the impingement position on the detection area are employed for the curve fitting. 
     
     
       27. The device according to  claim 25 , wherein the reflector arrangement is configured as a prism selected from the group consisting of a Porro prism and a triple prism. 
     
     
       28. The device according to  claim 23 , wherein the curve fitting is to an ellipse. 
     
     
       29. The device according to  claim 24 , wherein the curve fitting is to an ellipse. 
     
     
       30. The device according to  claim 26 , wherein the curve fitting is to an ellipse. 
     
     
       31. A method for determining the position of a first shaft and of a second shaft that is joined to the first shaft by means of a coupling, comprising the steps of:
 placing a first measurement unit on a circumferential surface of the first shaft; 
 placing a second measurement unit on a circumferential surface of the second shaft; 
 producing at least one light beam bundle by at least one of the two measurement units and directing the at least one light beam bundle onto at one least one detection area on at least one of the two measurement units, 
 detecting data relating to the impingement position of the light beam bundle on the at least one detection area in a plurality of measured positions and detecting data relating to an angle of rotation of the shafts by at least one of the two measurement units by means of at least one sensor, which includes at least one biaxial accelerometer or one gyroscope; 
 wherein the respective angle-of-rotation position, angular velocity, and angular acceleration of the shafts are determined from data from the sensors and the respective impingement position of the light beam bundle on the at least one detection area is determined from the impingement position data, and offset of the shafts is determined from at least a part of the determined impingement positions by curve fitting; 
 performing a quality rating of the associated data for each of the individual measured positions based on at least the following criteria:
 angular velocity and angular acceleration, 
 difference between the tangential component of the impingement position and the tangential component of the impingement position of a preceding measured position, in relation to the time interval from the preceding measured position, 
 degree of deviation of the impingement position(s) from a curve fitted to at least a part of the determined impingement positions; and 
 
 excluding data of a measured position from consideration in determining the shaft offset or are considered only with reduced weighting if the quality rating of the data lies below a threshold value.